It's a memory-destroying disease that has baffled scientists for decades, but one researcher has a controversial theory: that we can catch it with a kiss.

Rich P. is only in his 20s, but these days he finds himself obsessing over something most guys his age never think twice about: Am I doomed to lose my mind?

In some ways, Rich's anxiety is understandable. "My girlfriend is a social worker who works with the aged, specifically people with Alzheimer's," he says. "So I've seen close up what the disease does to you." Indeed, Alzheimer's disease is characterized by memory loss and confusion, and typically ends with complete disconnection from the world. People in its advanced stages can't care for themselves, recognize loved ones, or remember the lives they lived.

There's also another, even more personal connection for Rich: His girlfriend's father recently passed away from Alzheimer's. He was one of more than 70,000 Americans who die from the disease every year.

Still, what should worry Rich most isn't what he's witnessed in other people, but what he sees in the mirror. Because there, literally right under his nose, is evidence that the monster that could be responsible for Alzheimer's is already skulking about inside his body, preparing itself—at some point, decades down the road—to attack and destroy his brain.

So here's the question: Is it in you too? For years, physicians and Alzheimer's experts have said that the earliest symptoms of the disease typically don't appear until you're in your 60s, 70s, or beyond. But now there's reason to believe that the first warning signs may actually crop up much earlier than that, and in a seemingly much more benign way: as cold sores, those embarrassing blisters that can erupt on the lips of people who are sick or run-down.

The sores are triggered by the herpes virus—most often, herpes simplex virus type 1 (not to be confused with HSV-2, which predominately causes genital herpes). In recent years, a growing body of research, much of it championed by a British scientist, has begun to suggest a startling fact: The same virus known for sabotaging people's social lives could be responsible for the majority of Alzheimer's cases.

"There's clearly a very strong connection," says the researcher, Ruth Itzhaki, Ph. D., speaking one afternoon in her office at the University of Manchester, in northwestern England. A neurobiologist, Itzhaki has spent the better part of two decades studying the link between herpes and Alzheimer's. "I estimate that about 60 percent of Alzheimer's cases could be caused by the virus."